1. Field of the Invention
The present invention relates to charging systems for use in communications.
2. Related Art
A fundamental problem in providing a communications network infrastructure is the ratio of peak to mean demand. The network infrastructure has to be dimensioned to deal with peak demand. This means that resources are not profitably utilised when demand lies below its peak.
In cellular communications systems, or mobile communications systems, demand can pose a significant problem. The number of customers has increased extremely fast. In the UK, there were about one million customers in 1990. By 1996, there were over six million connections to mobile networks.
Cellular, or mobile, communications networks have become established over the decade between the mid-80s and the mid-90s. There are various types, including analogue and digital signalling versions. Technical information about such networks has been published for instance in xe2x80x9cMobile Radio Telephones in the UKxe2x80x9d by Dr R. C. V. Macario, published in the UK by Glentop Press Ltd in 1988, in the British Telecom Technology Journal, Volume 8, No.1, January 1990, and in the British Telecom Technology Journal, Volume 14, No.3, July 1996. Two articles in the last quoted reference which may be particularly of interest are xe2x80x9cMobile Network Design and Optimisationxe2x80x9d by Button, J et al, at pages 29 to 46, and xe2x80x9cGlobal System for Mobile Communicationsxe2x80x94What""s in Store?xe2x80x9d by Holley, K A, at pages 47 to 54.
Referring to FIG. 1, a mobile network operator provides a set of signal transmitters 2 for communicating, usually by radio, with a mobile unit carried by the customer 10. The signal transmitters 2 are connected to switching units 3 of a land-based network, for instance the Public Switched Telecommunications Network (PSTN), on which the mobile network operator leases capacity. All long distance traffic is generally carried by the fixed network. It is primarily the customer access links, provided by the signal transmitters 2, which give the mobility.
The xe2x80x9ccellsxe2x80x9d of a cellular network are generally created as follows. The mobile customer receives signals from the network from any of a plurality of signal transmitters. In known networks of this type, the customer receives signals from the transmitter providing the strongest signal. This is usually but not necessarily the nearest transmitter. The plurality of transmitters thereby effectively creates cells, the boundary of each cell being the point at which the cell""s transmitter xe2x80x9chands overxe2x80x9d to an adjoining transmitter because the signal of the adjoining transmitter becomes stronger at that point.
It is not essential that the signal transmitters are all at permanently fixed locations. For instance, it is possible to use a mobile transmitter, even another mobile phone, as a signal transmitter to a mobile phone. That is, as long as it is not in use as a telephone, one mobile phone can act as a mobile xe2x80x9crepeaterxe2x80x9d for another mobile phone. In this way, one can install something to operate as a signal base station, even within a vehicle such as a bus.
In each cell, there will be several factors affecting availability of communications bandwidth to the user. These will include facilities provided, such as the capacity of available bearers, together with the traffic load already carried in a cell. Hence, in Britain the available capacity to users driving on the M25 motorway might be quite low, particularly at certain times of day, in spite of high capacity transmitters being available. Then in cells to either side of the M25 motorway, although the transmitters may have much lower bandwidth specifications, the available capacity might be relatively high because of the lower population of users in those adjacent cells.
It is possible to provide real-time pricing information to a user and a system for doing so in relation to a fixed network is set out in the specification of co-pending International patent application number WO94/28683. However as the user moves from cell to cell of a mobile network, the real-time pricing information can quickly become out of date and/or inappropriate.
According to a first aspect of the present invention, there is provided a charge control system for use in a cellular communications network infrastructure, wherein local charges are modifiable in response to current local traffic loading, the system comprising:
i) monitoring means for monitoring current local traffic loading in the network;
ii) a data store for storing historic traffic data related to cells of the network;
iii) data processing means for generating a local traffic-related parameter, dependent on the current traffic loading and the historic traffic data; and
iv) charge setting means for setting the rate at which traffic is charged by the network in a local area thereof, the rate set by the charge setting means being controlled at least in part by said local traffic-related parameter.
Embodiments of the invention may find application in fixed networks having an area-based management infrastructure, which therefore could be described as cellular. However, they are probably of more immediate relevance to networks which are designed at least in part for use by mobile users, such as the cellular mobile network provided in the UK by Cellnet. In this case, the historic traffic data usefully includes or comprises handover data, relating to historic handover patterns between cells.
Because the charge-setting depends at least in part on historic traffic data, it is possible to introduce a learning behaviour in the way charges are set.
Charge setting may be actually carried out in more than one way. For instance, it might be done by setting a field in a call record, during call set-up, to show an applicable charge rate for the duration of the call. In the known Cellnet mobile network, information specific to a user is usually stored at the Visiting or Home Location Registers. Information about usage, which will be billed to a particular user, is collected there in the form of toll tickets. A particularly convenient way of collecting billing information in embodiments of the present information, so that the charge rate for a call is maintained throughout the duration of a call, including across cell boundaries, might be to set a field in the toll ticket, at call set-up, which indicates a charge band. That field need only be modifiable thereafter under extraordinary circumstances, or perhaps with the agreement of the user. A charge band may be one of, for instance, 100 contiguous charge bands to give sufficient flexibility in the pricing structure.
Traffic will be carried, and charged, in different ways. A purpose of being able to set the charge rate is to influence the use of finite resources in a network. Depending on the access technology used, the xe2x80x9cfinite resourcexe2x80x9d might be channel frequencies, available time slots or, in Code Division Multiple Access (CDMA), simply the number of users communicating in a common geographical area.
(It should be noted that although reference may be made herein to xe2x80x9ccallsxe2x80x9d, this should be taken to mean any connection using the network which can be expected to be billed. It therefore covers data transfer, telemetry and multimedia applications for instance, not necessarily involving voice.)
Embodiments of the invention will find particular relevance in cellular mobile networks.
Preferably, the charge control system further comprises reporting means to report current charge rate information to user equipment. For instance, it may broadcast current local charge rates to all user equipment which is switched on. However, that approach uses a relatively high level of capacity. A charge rate report might be triggered by a user input, such as a specific request or simply putting their equipment in the xe2x80x9coff hookxe2x80x9d condition, to transmit the report just to that user. A third and perhaps best alternative is that the reporting means sends charge rate reports to each user whose equipment is switched on, in turn, using perhaps an existing control channel or, in digital links, an allocated time slot of the connection channel. The charge rate report could include a string of charge rates, each relevant to a different type of communication that the user might be interested in, such as both single and multiple channel charge rates.
Current charge rate information can be used by the user in deciding whether or not to make a call.
Preferably also, the charge control system will further comprise means to peg a local charge rate for the duration of a connection established by a user. This may be done as mentioned above, during call set-up. The pegging is preferably maintained even if the user moves to a different cell. Alternatively, the system might notify any current users of impending charge rate changes. The users could then make a decision to terminate or postpone a connection. This alternative might only be used in unusual circumstances, such as heavy build of traffic in a cell during data download by a user, since it is likely to be preferred by the user that a connection can be continued at fixed rate, once started.
Systems built according to embodiments of the present invention can control local charge rates so as to take into account not only the resources available at a customer""s current location, but also the resources available at one or more potential locations for that customer. Preferably, the data processing means, in generating a charge rate for a cell, calls up traffic loading data for that cell, and for its neighbours, and applies an algorithm which includes terms for traffic loading data at the customer""s current location and at one or more potential locations for that customer.
The data processing means may call up handover data giving at least a relative probability of handover to each of the neighbouring cells and use these relative probabilities to weight the importance given to the traffic loading data for each of the neighbouring cells in generating a local charge rate.
Alternatively or additionally, systems according to embodiments of the present invention might take into account the current and future expected traffic loading in one cell, in the light of traffic which can be expected to be incoming to the cell, newly arising there, and perhaps also outgoing from the cell.
A suitable form of algorithm might be used to generate the local traffic-related parameter by calculating a value taking into account available resources, expressed as Free Bandwidth (FBW), as follows:                     FBW        =                  xe2x80x83                ⁢                              (                          total              ⁢                              xe2x80x83                            ⁢              capacity              ⁢                              xe2x80x83                            ⁢              of              ⁢                              xe2x80x83                            ⁢              a              ⁢                              xe2x80x83                            ⁢              cell              ⁢                              xe2x80x83                            ⁢              A                        )                    -                                                  xe2x80x83                ⁢                  ∑                      xe2x80x83                    ⁢                                    (                                                prob                  .                                      xe2x80x83                                    ⁢                  of                                ⁢                                  xe2x80x83                                ⁢                handover                ⁢                                  xe2x80x83                                ⁢                from                ⁢                                  xe2x80x83                                ⁢                cell                ⁢                                  xe2x80x83                                ⁢                k                ⁢                                  xe2x80x83                                ⁢                into                ⁢                                  xe2x80x83                                ⁢                cell                ⁢                                  xe2x80x83                                ⁢                A                            )                        *                                                            xe2x80x83                ⁢                              (                          calls              ⁢                              xe2x80x83                            ⁢              in              ⁢                              xe2x80x83                            ⁢              progress              ⁢                              xe2x80x83                            ⁢              in              ⁢                              xe2x80x83                            ⁢              cell              ⁢                              xe2x80x83                            ⁢              k                        )                    -                                                  xe2x80x83                ⁢                  average          ⁢                      xe2x80x83                    ⁢          number          ⁢                      xe2x80x83                    ⁢          of          ⁢                      xe2x80x83                    ⁢          calls          ⁢                      xe2x80x83                    ⁢          received          ⁢                      xe2x80x83                    ⁢          in          ⁢                      xe2x80x83                    ⁢          a          ⁢                      xe2x80x83                    ⁢          time          ⁢                      xe2x80x83                    ⁢          period          ⁢                      xe2x80x83                    ⁢          in                ⁢                  xe2x80x83                                                  xe2x80x83                ⁢                  cell          ⁢                      xe2x80x83                    ⁢          A                    
(The symbol xe2x80x9c*xe2x80x9d is used herein to indicate multiply.)
The summation in the above will generally be over all the neighbouring cells k=1,2,3 . . . . Usually, in known cellular networks for instance of the type provided by Cellnet in the UK, there will be six neighbouring cells. However, in some circumstances the probability of handover to a neighbouring call might be so low that it can effectively be ignored. This might for instance be the case for calls adjacent to the M25 motorway which map onto fields.
To take into account loss of calls from cell A, a further term can be added. This will be a weighted value of the term:
(prob of handout or call termination in a time period)*(calls in progress)
The actual charge rate set will of course be a function of FBW and could simply be an inverse relationship. However, it is extremely useful to be able to introduce a more complex relationship. This is because there will be coupling between the charge rates notified to users and the take-up rate, or extent to which users then choose to establish calls. Preferably then, the data processing means applies a selected function to FBW to generate the actual charge rates to be output.
Preferably of course, this selected function can be modified, for instance in the light of experience or changing patterns of behaviour.
The above algorithm for FBW can be further modified, as will be described below. Particularly, there may be added a term which prevents FBW rising above a threshold, the threshold being controlled by the neighbouring cell with the worst relationship between available capacity and probability of receiving handover from cell A.
Although the charge rate might be for a unit of connection time, it could be set in different ways. The charge rate is simply for a communications resource. It could alternatively be for instance for a unit of bandwidth, or number of bits transmitted in a variable bit rate service.
Embodiments of the present invention provide a practical, substantially real-time, control mechanism which not only controls the network charging mechanism but can be used by the network infrastructure provider to influence demand such that it is better optimised across the network rather than simply in relation to a single cell of the mobile network. The demand is influenced by supplying the price information to the customer in advance of the customer deciding to make a call. They may decide to wait until they reach a cell where the price is lower. This optimises demand because the cheaper calls will be those with more available capacity. It would also be possible to advise the customer of locations where the price will be lower and so directly encourage them to wait, or indeed to decide to move to such a location.
Another advantage of embodiments of the present invention is that, because the available capacity of adjacent cells is taken into account, the customer can be effectively forewarned of call blocking if an adjacent cell is fully loaded. If only the customer""s current cell is taken into account when a call is first established, the call may later be blocked on handover to a neighbouring cell. Embodiments of the present invention can reduce the occurrence of that happening, at least between a neighbouring pair of cells.